Electric vehicles (EV) and hybrid electric vehicles (HEV) obtain optimal fuel economy largely by means of electric propulsion, wherein a high-voltage battery, working in conjunction with one or more onboard electric motor/generators and/or an offboard electrical power supply, provides the required propulsive energy. For example, a typical full HEV can selectively utilize a high-voltage battery module or energy storage system (ESS) as a propulsive energy source during conditions under which an electric motor is relatively efficient, automatically transitioning to propulsion via an internal combustion engine at higher speeds. Likewise, an extended-range EV equipped with a suitable high-voltage ESS can operate exclusively using electric power.
In addition to the distinct performance advantages of using an electric motor as a vehicular propulsion device, an electric motor can operate almost noiselessly, i.e., without the familiar combustion and fan sounds generated by a conventional gasoline-powered internal combustion engine. As a result, the relatively tranquil environment in an EV or HEV interior can be another desirable feature of such vehicle designs. However, for other drivers the familiar engine sounds can be desirable during all operating modes. Therefore, in order to optimize the driving experience some modern vehicles are adapted to synthesize or broadcast engine sounds in response to throttle and/or speed signals, such as by generating the sound of a sporty or high-performance engine during an electric drive mode.
Additionally, certain vehicles are configured to transmit or broadcast synthesized engine noises or other warning sounds outside of the vehicle when propelled via electric power in order to alert pedestrians, cyclists, and other persons or animals in the path of or in close proximity to the otherwise nearly silent vehicle. While such synthesized sounds have notable advantages, the perception of synthesized sounds within the vehicle interior may be undesirable to some drivers and passengers, particularly those who highly value the relative tranquility of electric propulsion.